Coupling Types - Kinematic Couplings

The fully kinematic coupling represents the gold standard
of couplings by using individual point contacts that each constrain a
single degree of freedom. Because the interaction between the interface
surfaces can be described by six distinct points, closed loop mathematics
can be formulated to deterministically describe the relationship between
the surfaces. In reality, point contacts must typically tolerate high
loads, therefore the theoretical point contacts deform into Hertzian contact
ellipses under large applied loads. The main limit to the repeatability
of a kinematic coupling is the surface finish of the contact regions,
while load capacity and stiffness are limited by the Hertzian contact
stress.

By far, the most common form of the standard kinematic coupling is the
ball- groove coupling, which interfaces three balls on one component to
three grooves on the opposing component. The balls and grooves are placed
on the three points of a planar equilateral triangle with the triangle
sides coincident to lines passing through the contact points. The typical
coupling structure is shown below with the standard coupling geometry
terminology.

Three Ball - Three Groove Coupling

Standard Coupling Geometry

More information on the design and use of kinematic couplings
can be found in following pdf documents: